Estonian Patent application No. P201000069 describes a method for the production of disinfectants and an electrolyzer for the execution of the method disclosed therein, in which part of a fresh water flow is used both for cooling a cathode compartment and for the reduction of the concentration of active chlorine in a co-mixer of the electrolyzer. A drawback to this method is that the flow rate passing through the cathode compartment (0.4-0.8% of the disinfectant flow) remains below 2.4 liters per hour (L/h) in devices with a low capacity (up to 300 liters per hour) and it requires the attention of personnel or the use of pressure pumps. Patents RU 2297980 and U.S. Pat. No. 5,985,110 disclose methods using a cylindrical diaphragm electrolyzer and the solution of sodium chloride as an electrolyte. In the method disclosed in RU 2297980, the whole flow of fresh water is mixed with sodium chloride and after mixing, the flow is divided between anode and cathode compartments in a selected ratio, turning the flows into anolyte and catholyte, respectively. Anolyte functions as a disinfectant, while catholytehas often no applications. The pH value of the disinfectant is adjusted in a range from 2.5 to 5.5 by changing the ratio between the flows from the anode and cathode compartments.
In method disclosed in U.S. Pat. No. 5,985,110, the whole flow of fresh water is mixed with sodium chloride; after mixing, the whole flow is guided to a cathode compartment. After flowing out from the cathode compartment and the electrolyzer, some of the catholyte is guided to waste and the rest of the catholyte to the anode compartment. From the anode compartment comes out anolyte, which forms the disinfectant. The pH value of the disinfectant is adjusted in the range from 5.5 to 8.5 of the discharged catholyte, meaning changing the ratio between the flows passing through the anode and cathode compartments. A circumstance that arises from these known methods, and which could be considered a common drawback to methods disclosed in RU 2297980 and U.S. Pat. No. 5,985,110 is that the solution of sodium chloride passing through the anode compartment has a low level of mineralization (up to 8 g/l—a quantity equal with the quantity of the produced disinfectant), resulting in the consumption of over 30 W of electrical energy and 12 g of sodium chloride for the production of 1 g of active chlorine. What is needed is a method to reduce mineralization arises from the aspect that with the equal concentration of active chlorine and pH level, the best disinfectants by their bactericidal and corrosion preventive effect are substances with a lower content of sodium chloride. Reducing the consumption of sodium chloride per 1 g of active chlorine with the known methods disclosed in RU 2297980 and U.S. Pat. No. 5,985,110 would mean the reduction of anode and cathode flows, an increase in the electrical resistance between electrodes, a decrease in current intensity and a shortage of electrical energy for the production of the required quantity of active chlorine. Traditionally, these problems are solved by: increasing the voltage of electrodes, reducing the distance between electrodes and using a thinner membrane, multiple circulation of flows through the electrode compartments together with the use of external cooling equipment, and several consecutive electrolyzers to reduce the flow rate passing through one electrolyzer. The technical solutions for the reduction of the consumption of sodium chloride are described in more detail for example in patents RU 2130786, RU 2248940, RU 2350692, WO 2006098660 and U.S. Pat. No. 5,783,052; however, with all these solutions the electrolyzers, equipment and methods become substantially more complex.
The equipment necessary for the execution of the methods disclosed in RU 2297980 and U.S. Pat. No. 5,985,110 are described for example in patents RU 2079575 and U.S. Pat. No. 5,871,623. The parts of devices RU 2079575 and U.S. Pat. No. 5,871,623 are as follows: a cylindrical diaphragm electrolyzer with coaxially located anode, cathode and membrane; a source of electrical energy, a supply pipe for fresh water, a mixing unit for fresh water and sodium chloride, a supply pipe to feed sodium chloride to electrode compartments in a quantity that equals with the summed amount of produced disinfectant and disposed catholyte; and valves for adjusting the ratio of flows passing through the anode and cathode compartments. In the device disclosed in U.S. Pat. No. 5,871,623 there is also a discharge for catholyte after flowing out from the electrolyzer and before the anode compartment. The drawback to these prior art devices is that each one of these is designed for realizing only one method—either the method disclosed in RU 2297980, which yields a disinfectant with the pH value from 2.5 to 5.5, or the method disclosed in U.S. Pat. No. 5,985,110, which yields a disinfectant with the pH value from 5.5 to 8.5; at this the same consumer may need simultaneously disinfectants with different pH values in case of a different technology, obtained on the basis of the diaphragm electrolysis of sodium chloride. For example, a farmer is recommended to use a disinfectant with the pH value 3.0-3.5 in the pre-sowing treatment of grain seeds, a pH value 7.0-8.5 in disinfecting the milking equipment, a pH value 2.5-3.5 in the production of silage, and a pH value 6.0-7.5 in disinfecting the drinking water of animals for fattening, etc. Thereby, in practical activities, a relatively wide pH range is required. In addition, the design of electrolyzers used in the known methods of RU 2079575 and U.S. Pat. No. 5,871,623 does not allow the reduction of the consumption of sodium chloride without having applied external circulation and cooling circuits or supplementary electrolyzers. An additional drawback to the equipment used to employ these known methods is that external factors have a major impact on the execution of the method: a random increase in supply voltage entails a change in the quality of the disinfectant and failure of the device, switching on the device involves possible current surges and the supply may be automatically switched off, which may not always be noticed by the operator and the device produces to the collection tank, brine instead of the disinfectant.